The current leading cause of death in the United States is coronary artery disease (CAD) which is the occlusion or blockage of the coronary arteries by atherosclerotic plaques or fatty deposits. Occlusions in the coronary arteries generally causes chest pain (angina) and/or heart attacks (myocardial infarction) due to a lack of blood flow, i.e. oxygen, to the tissues of the heart. The lack of oxygen in tissues of the heart causes myocardial ischemia. Severe and prolonged myocardial ischemia can produce cardiac dysfunction, heart muscle damage and possibly death.
One treatment to relieve a partially or fully blocked coronary artery is coronary artery bypass graft (CABG) surgery. CABG surgery, also known as “heart bypass” surgery, generally entails the use of a graft or conduit to bypass the coronary obstruction and, thereby provide blood flow to the downstream ischemic heart tissues. More particularly, a fluid connection or “anastomosis” is surgically established between a source vessel of oxygenated blood and the obstructed or restricted target coronary artery downstream or distal to the obstruction or restriction to restore the flow of oxygenated blood to the heart muscle. In one approach, the surgeon attaches an available source vessel, e.g., an internal mammary artery (IMA), directly to the obstructed target coronary artery at the distal anastomosis site downstream from the obstruction or restriction.
Conventional CABG procedures are typically conducted on a cardioplegic arrested heart while the patient is on cardiopulmonary bypass (CPB). A stopped heart and a CPB circuit enable a surgeon to work in a relatively motionless, bloodless operative field, however there are a number of problems associated with CABG procedures performed while on CPB. For example, problems associated with conventional CABG procedures may include the initiation of a systemic inflammatory response due to the interactions of blood elements with the artificial material surfaces of the CPB circuit, global myocardial ischemia due to global (hypothermic) cardiac arrest, and post-operative stroke due to clamping of the aorta. In addition, the use of a partial side-biting aortic clamp used to isolate a portion of the aorta can also cause trauma to the patient. The use of clamps can add to the time required for performing the procedure, as well as the use of clamps may dislodge plaques from the vessel being clamped resulting, for example, in neurologic injury. The clamping pressure can also cause damage to the endothelial lining of the aorta. Post-operative scarring can provide an irregular surface causing increased plaque build up.
Obstructed coronary arteries are generally bypassed; for example, with an in situ internal mammary artery (IMA) or a reversed segment of saphenous vein harvested from a leg. Segments of other suitable blood vessels may also be used for grafting depending on availability, size and quality. In general, the body hosts seven potential arterial conduits, the right and left IMAs, the radial arteries and three viceral arteries, one in the abdomen, and two in the lower abdominal wall, though the latter may be quite short and are generally of limited usefulness. The viceral arteries include the gastroepiploic artery and the splenic artery.
The left IMA is best used for bypass to the left anterior descending (LAD) coronary artery and its diagonal branches. Whereas, the right IMA may be used for bypass to selected vessels more posterior such as the distal right coronary artery (RCA). The right IMA may also be used for bypass to selected marginal branches of the left circumflex coronary artery. A segment of radial artery harvested from an arm is generally used to revascularize the posterior surface of the heart. The right gastroepiploic artery may be used to revascularize almost any artery on the surface of the heart. It is most commonly used for bypass to the distal RCA or the posterior descending coronary artery. In unusual circumstances the splenic artery is used to revascularize posterior coronary arteries, but it is long enough to reach the marginal branches of the circumflex coronary artery.
Surgeons generally complete bypass grafts to the following coronary arteries in a patient undergoing multiple bypass surgery in roughly the following order: posterior descending coronary artery (PDA), RCA, obtuse marginal branch, circumflex coronary artery, diagonal branch, and LAD. More generally, surgeons will revascularize the three coronary systems in the following order: right, circumflex, and anterior descending. However, the order may vary depending on whether the procedure is performed on a beating heart or an arrested heart. For arrested heart, about 3 to 4 bypass grafts of which 1 to 3 are free grafts are generally performed per procedure. In contrast, about 2 to 3 bypass grafts of which 0 to 2 are free grafts are generally performed per beating heart procedure. In general, 1 free graft is used per beating heart procedure.
When a saphenous vein or other blood vessel is used as a free graft in a procedure, two anastomoses are performed; one to the diseased artery distal to the obstruction (outflow end), and one proximally to the blood vessel supplying the arterial blood (inflow end). These anastomoses are generally performed using end-to-side and/or side-to-side anastomotic techniques. Rarely an end-to-end anastomotic technique is used. When more than one graft is required in any of the three coronary systems for complete revascularization of the heart, sequential graft techniques may be used to conserve the amount of blood vessels required. Sequential graft techniques use proximal side-to-side anastomoses and an end-to-side anastomosis to complete the graft. For example, a common sequence used in the anterior descending coronary system is a side-to-side anastomosis of graft to the diagonal branch and an end-to-side anastomosis of graft to the LAD coronary artery.
The majority of surgeons will complete the distal anastomosis of a graft prior to completion of the proximal anastomosis. The small percentage of surgeons who do complete the proximal anastomosis first usually do so to allow antegrade perfusion of cardioplegic solution through the graft during revascularization. Construction of the distal anastomosis, e.g., a saphenous vein-coronary artery anastomosis, begins by first locating the target artery on the heart. Next, an incision is made through the epicardium and the myocardium to expose the artery. An arteriotomy is then made using a knife to incise the artery. The incision is then extended with a scissors. The length of the incision approximates the diameter of the saphenous vein, about 4 to 5 mm. The diameter of the target artery is generally 1.5 to 2.0 mm. Since, most surgeons feel the distal take-off angle should be 30 to 45 degrees, the distal end of the saphenous vein is beveled at about 30 to 45 degrees.
Most surgeons construct the anastomosis via a ten-stitch running suture using 7-0 polypropylene suture material. The ten-stitch anastomosis typically comprises five stitches around the heel of the graft and five stitches around the toe. The five stitches around the heel of the graft comprise two stitches to one side of the apex of the graft and the artery, a stitch through the apex and two stitches placed at the opposite side of the apex. The graft is generally held apart from the coronary artery while the stitches are constructed using a needle manipulated by a forceps. Suture loops are drawn up and the suture pulled straight through to eliminate purse-string effect. The five stitches around the toe of the graft also comprises two stitches to one side of the apex of the graft and the artery, a stitch through the apex and two stitches placed at the opposite side of the apex. Again, suture loops are drawn up and the suture pulled straight through to eliminate purse-string effect. The suture ends are then tied.
The proximal anastomosis of a saphenous vein graft to the aorta, i.e., an aortosaphenous vein anastomosis, is generally formed by first removing the pericardial layer that covers the aorta. An occluding or side-biting clamp may be placed on the aorta at the anastomosis site. A small circular or elliptical portion of the ascending aorta is excised forming a small opening 4 to 5 mm in diameter. An aortic punch typically facilitates this procedure. The opening for a right-sided graft is made anterior or to the right lateral side of the aorta, whereas an opening for a left-sided graft is made to the left lateral side of the aorta. If the graft is to supply blood to the right coronary artery, the opening is made proximal on the aorta. If the graft is to supply blood to the anterior descending coronary artery, the opening is made in the middle on the aorta. And, if the graft is to supply blood to the circumflex artery, the opening is made distal on the aorta. The right graft opening is placed slightly in the right of the anterior midpoint of the aorta and the left graft opening slightly to the left. The end of the saphenous vein is cut back longitudinally for a distance of approximately 1 cm. A vascular clamp is placed across the tip of the saphenous vein to flatten it, thereby exposing the apex of the vein. Five suture loops of a running suture using 5-0 polypropylene are then placed around the ‘heel’ of the graft and passed through the aortic wall. Two stitches are placed on one side of the apex, the third stitch is placed precisely through the apex of the incision in the saphenous vein, and the final two stitches are placed on the opposite side of the apex. Suture traction is used to help expose the edge of the aortic opening to ensure accurate needle placement. Stitches include about 3 to 5 mm of the aortic wall for adequate strength. Suture loops are then pulled up to approximate the vein graft to the aorta. The remaining stitches are placed in a cartwheel fashion around the aortic opening thereby completing the remainder of the anastomosis.
Left-sided grafts are oriented so the apex of the incision in the “heel” of the saphenous vein will face directly to the left side. The stitches are placed in a clockwise fashion around the heel of the graft and in a counterclockwise fashion around the aortic opening. Right-sided grafts are oriented in a caudal fashion. The stitches are placed in a counterclockwise fashion around the heel of the graft and in a clockwise fashion around the aortic opening. Five suture loops complete the heel portion of the graft and an additional five or six are necessary to complete the toe of the graft. Finished proximal anastomoses usually have a “cobra-head” appearance.
It is essential for the surgeon to take steps to minimize the possibility of thrombosis, narrowing and/or premature closure of the anastomosis due to technical errors. Some surgeons feel the proximal anastomosis must have a take-off angle of 45 degrees while other surgeons believe the take-off angle is not critical. In addition, it is generally felt that intima-to-intima contact of the vessels at the anastomosis is advantageous for endothelization to occur, thereby making an ideal union of the vessels. However, intima-to-adventitia contact is acceptable by most surgeons. The main objective of the surgeon is to create an anastomosis with an expected long-term patency rate of greater than 5 to 10 years. The creation of an anastomosis takes approximately 10 to 15 mins.
One essential requirement for creating a sutured anastomosis without error is adequate exposure. Acute visualization of the vessel walls is mandatory in order to properly place each stitch and avoid inadvertently including the back wall of the vessel in a stitch, which in effect narrows or completely occludes the vessel. In order to achieve the required exposure most surgeons will employee blood-less field devices such as shunts, snares, and misted blowers. Further, largely invasive surgical techniques are also employed to help the surgeon gain access to the grafting site. For this reason, CABG surgery is typically performed through a median stemotomy, which provides access to all major coronary branches. A median stemotomy incision begins just below the sternal notch and extends slightly below the xiphoid process. A sternal retractor is used to separate the sternal edges for optimal exposure of the heart. Hemostasis of the sternal edges is typically obtained using electrocautery with a ball-tip electrode and a thin layer of bone wax.
Currently, the golden standard for creation of a vascular anastomosis is manual suturing. Manual suturing may be used to attach vascular grafts (either autografts or prosthetic grafts) for coronary bypass, femoral-femoral bypass (to relieve inadequate circulation in the legs), and AV fistulas and/or shunts (access portals for repeated puncture applications such as kidney dialysis or diabetes). However, a number of cardiac surgical procedures, e.g., off-pump, beating heart CABG procedures, minimally invasive procedures and even totally endoscopic procedures with access through ports only, may require a variety of new anastomotic techniques. The ability of performing anastomoses with limited or no CPB support may increase the possibility of performing more CABG procedures using minimally invasive surgical techniques. Avoiding the use of cross clamps and CPB or dramatically reducing pump run and cross clamp times may effectively minimize post-operative complications. For this reason, there is an increasing need for easier, quicker, less damaging, but reliable automated, semi-automated, or at least facilitated methods to replace or enhance the normal process of a manually sutured vascular anastomosis.
The major objective of any CABG procedure is to perform a technically perfect anastomosis. However, creation of a technically perfect anastomosis is generally complex, tedious, time consuming and its success is highly dependent on a surgeon's skill level. Therefore, creation of vascular anastomoses without the need to perform delicate and intricate suture lines may enable surgeons to more quickly create simpler and effective anastomoses. Currently, there are a number of techniques or procedures being investigated for facilitating the process of forming an anastomosis including vascular clips or staples, glues, adhesives or sealants, laser welding, mechanical couplers, stents and robot-assisted suturing. These techniques are being developed for performing end-to-end, end-to-side and/or side-to-side anastomoses with or without temporary blood flow interruption. In general, these techniques may include the use of various biomaterials and/or biocompatible agents.
There are a number of alternative approaches to CABG surgery. In one approach, the surgeon harvests a graft blood vessel from the patient and prepares its proximal and distal ends to be attached in a “proximal anastomosis” and a “distal anastomosis” bypassing the occlusion. This type of graft is commonly known as a “free” graft. The proximal anastomosis can be located proximal or upstream to the occlusion or to another vessel supplying oxygenated blood, e.g., the aorta. Typically, a section of the saphenous vein or radial artery is harvested from the patient's body and used as a free graft. The opening in the aorta, the aortotomy, is typically made by removing the pericardial layer covering the aorta, creating a small (less than 5 mm) incision through the layers of aortic wall, inserting an aortic punch into the incision and finally actuating the punch to create a round hole. This hole is made into the aorta to provide arterial blood to the bypass graft. To achieve the best flow dynamics, the hole created by the punch should have smooth edges. In addition, the aortic tissue may be very tough to puncture, thereby requiring some effort to produce an acceptable aortotomy.
In another approach, a portion of the left IMA or right IMA is dissected away from supporting tissue and severed so that the severed end can be anastomosed to the obstructed coronary artery distally to the stenosis or occlusion. More recently, other arteries have been used in “attached” graft procedures, including the inferior epigastric arteries and gastroepiploic arteries. It is also stated in U.S. Pat. No. 6,080,175 that a conventional electrosurgical instrument can be introduced through a port or incision and used to dissect and prepare the bypass graft vessel for coronary anastomosis while viewing the procedure through a thoracoscope.
It is necessary to access and prepare the site or sites of the vessel wall of the target coronary artery where the proximal and/or distal anastomosis is to be completed and to then make the surgical attachments of the blood vessels. First, it is necessary to isolate the anastomosis site of the target coronary artery from the epicardial tissues and overlying fatty layers. Typically, blunt, rounded #15 scalpel blades are employed to dissect these tissues and layers away from the target coronary artery.
Generally, blood flow in the target coronary artery is interrupted by, for example, temporary ligation or clamping of the artery proximal and/or distal of the anastomosis site, and the target coronary artery wall is opened to form an arteriotomy, that is, an elongated incision at the anastomosis site extending parallel to the axis of the coronary vessel and equally spaced from the sides of the coronary artery that are still embedded in or against the epicardium. The arteriotomy is typically created by use of a very sharp, pointed, #11 scalpel blade to perforate the coronary artery wall, and the puncture is elongated the requisite length using scissors. A “perfect arteriotomy” is an incision that has straight edges, that does not stray from the axial alignment and equal distance from the sides of the coronary artery, and is of the requisite length.
Similarly, it is necessary to prepare the attachment end of the source vessel by cutting the source vessel end at an appropriate angle for an end-to-side or end-to-end anastomosis or by forming an elongated arteriotomy in the source vessel wall of a suitable length that is axially aligned with the source vessel axis for a side-to-side anastomosis. Typically, the surgeon uses surgical scalpels and scissors to shape the source vessel end or make the elongated arteriotomy slit in the source vessel, and uses sutures or clips to close the open severed end.
In the example depicted schematically in FIG. 1, the heart 12 is prepared as described above for an end-to-side anastomosis of the surgically freed, severed, and appropriately shaped vessel end 31 of the left IMA 30 branching from the aorta 16 and left subclavian artery 18 to the prepared arteriotomy 15 in the vessel wall of the left anterior descending (LAD) coronary artery 14 downstream from the obstruction 38. Similarly, in the example depicted schematically in FIG. 3, the heart 12 is prepared as described above for a side-to-side anastomosis of the left IMA 30 to the prepared arteriotomy 15 in the vessel wall of the LAD coronary artery 14. In the side-to-side anastomosis, an arteriotomy 33 is made in the freed segment of the left IMA 30, and the vessel end 31 is sutured closed. In the example depicted schematically in FIG. 5, the heart 12 is prepared as described above for an end-to-side anastomosis of the surgically harvested, and appropriately shaped vessel end 41 of the free graft 40, e.g., a saphenous vein or radial artery segment, to the prepared arteriotomy 15 in the vessel wall of the LAD coronary artery 14 downstream from the obstruction 38. In addition, the heart 12 is prepared as described above for an end-to-side anastomosis of the appropriately shaped vessel end 42 of the free graft 40 to the prepared aortotomy 43 in the wall of the aorta 16.
The prepared end or elongated arteriotomy of a bypass graft or source vessel is attached or anastomosed to the target coronary artery or aorta at the arteriotomy or aortotomy in a manner that prevents leakage of blood employing sutures, staples, surgical adhesives and/or various artificial anastomosis devices. For example, an end-to-side anastomosis 35 of the shaped vessel end 31 of the left IMA 30 to the prepared arteriotomy 15 in the vessel wall of the LAD coronary artery 14 is illustrated in FIG. 2. And a side-to-side anastomosis 37 joining the arteriotomy 33 of the left IMA 30 to the prepared arteriotomy 15 of the LAD coronary artery 14 is illustrated, for example, in FIG. 4. And an end-to-side anastomosis 35 of the shaped vessel end 41 of the free graft 40 to the prepared arteriotomy 15 in the vessel wall of the LAD coronary artery 14 is illustrated in FIG. 6. In addition, an end-to-side anastomosis 47 of the shaped vessel end 42 of the free graft 40 to the prepared aortotomy 43 in the wall of the aorta 16 is also illustrated in FIG. 6. Alternatively, anastomoses 35 and 47 may be constructed as side-to-side anastomoses, if so desired.
The inner, endothelial layer, vessel linings are less thrombogenic than the outer epithelial layers of blood vessels. So, in one approach, the attachment is made by everting and applying the interior linings of the bypass graft or source vessel and the target coronary artery against one another and suturing or gluing or otherwise attaching the interior linings together. Various types of artificial biocompatible reinforcement sleeves or rings may also be used in the anastomosis. Currently, a number of mechanical anastomotic devices, materials, techniques, and procedures are being developed for facilitating the process of forming an anastomosis including vascular clips or staples, glues, adhesives or sealants, laser welding, mechanical couplers, stents and robot-assisted suturing. These techniques are being developed for performing end-to-end, end-to-side and/or side-to-side anastomoses with or without temporary blood flow interruption. In general, these techniques can include the use of various biomaterials and/or biocompatible agents. See, for example, U.S. Pat. Nos. 5,385,606, 5,695,504, 5,707,380, 5,972,017 and 5,976,178, and 6,231,565.
Various examples of forming the target vessel arteriotomy or arteriotomies, the shaped end or side wall arteriotomy of the source vessel, and the positioning and attachment of the source vessel and target artery together are set forth in U.S. Pat. Nos. 5,776,154, 5,799,661, 5,868,770, 5,893,369, 6,026,814, 6,071,295, 6,080,175, 6,248,117, 6,331,158, and 6,332,468.
In a conventional bypass graft or CABG procedure, the surgeon exposes the obstructed coronary vessel through an open chest surgical exposure or stemotomy providing direct visualization and access to the epicardium. Typically, fat layers that make it difficult to see either the artery or the occlusion cover the epicardial surface and the obstructed cardiac artery. However, surgeons are able to dissect the fat away to expose the artery and manually palpate the heart to feel the relatively stiff or rigid occlusion within the artery as a result of their training and experience. The surgeon can determine the location and length of the occlusion as well as suitable sites of the target coronary artery for the proximal and distal anastomoses with some degree of success.
The open chest procedure involves making a 20 to 25 cm incision in the chest of the patient, severing the sternum and cutting and peeling back various layers of tissue in order to give access to the heart and arterial sources. As a result, these operations typically require large numbers of sutures or staples to close the incision and 5 to 10 wire hooks to keep the severed sternum together. Such surgery often carries additional complications such as instability of the sternum, post-operative bleeding, and mediastinal infection. The thoracic muscle and ribs are also severely traumatized, and the healing process results in an unattractive scar. Post-operatively, most patients endure significant pain and must forego work or strenuous activity for a long recovery period.
Many minimally invasive surgical techniques and devices have been introduced in order to reduce the risk of morbidity, expense, trauma, patient mortality, infection, and other complications associated with open chest cardiac surgery. Less traumatic limited open chest techniques using an abdominal (sub-xyphoid) approach or, alternatively, a “Chamberlain” incision (an approximately 8 cm incision at the stemocostal junction), have been developed to lessen the operating area and the associated complications. In recent years, a growing number of surgeons have begun performing CABG procedures while the heart is still beating using minimally invasive direct coronary artery bypass grafting (MIDCAB) surgical techniques and devices. Using the MIDCAB method, the heart typically is accessed through a mini-thoracotomy (i.e., a 6 to 8 cm incision in the patient's chest between the ribs) that avoids the stemal splitting incision of conventional cardiac surgery. A MIDCAB technique for performing a CABG procedure is described in U.S. Pat. No. 5,875,782, for example.
Other minimally invasive, percutaneous, coronary surgical procedures have been advanced that employ multiple small trans-thoracic incisions to and through the pericardium, instruments advanced through sleeves or ports inserted in the incisions, and a thoracoscope to view the accessed cardiac site while the procedure is performed as shown, for example, in the above-referenced '175, '295, '468 and '661 patents and in U.S. Pat. Nos. 5,464,447, and 5,716,392. Surgical trocars having a diameter of about 3 mm to 15 mm are fitted into lumens of tubular trocar sleeves or ports, and the assemblies are inserted into skin incisions. The trocar tip is advanced to puncture the abdomen or chest to reach the pericardium, and the trocar is then withdrawn leaving the port in place. Surgical instruments and other devices such as fiber optic thoracoscopes can be inserted into the body cavity through the port lumens. As stated in the '468 patent, instruments advanced through trocars can include electrosurgical tools, graspers, forceps, scalpels, electrocautery devices, clip appliers, scissors, etc.
In an endoscopic approach, the surgeon may stop the heart by utilizing a series of internal catheters to stop blood flow through the aorta and to administer cardioplegia solution. The endoscopic approach utilizes groin cannulation to establish CPB and an intraaortic balloon catheter that functions as an internal aortic clamp by means of an expandable balloon at its distal end is used to occlude blood flow in the ascending aorta. A full description of an example of one preferred endoscopic technique is found in U.S. Pat. No. 5,452,733, for example.
In an attempt to eliminate problems associated with CPB, “beating heart” procedures that eliminate the need for CPB have been developed. Surgical instruments that attempt to stabilize or immobilize a portion of the beating heart that supports the target coronary artery and the anastomosis site have been developed. These beating heart procedures and instruments described, for example, in the above-referenced '158, '175, '770, '782, and '295 patents and in U.S. Pat. Nos. 5,976,069, and 6,120,436, can be performed on a heart exposed in a full or limited thoracotomy or accessed percutaneously.
For example, a retractor assembly disclosed in the above-referenced '158 patent mounts to and maintains the chest opening while supporting a stabilizer assembly that extends parallel stabilizer bars against the epicardium alongside the target coronary artery so that force is applied across the anastomosis site to suppress heart motion. The surgeon employs conventional manually applied clamps to block blood flow through the arterial lumen and scalpels and scissors to make the elongated incision of the arteriotomy.
Instruments are disclosed in the above-referenced '295 patent that apply suction to the epicardial surface around or alongside the anastomosis site to suppress heart motion. Again, the surgeon employs the conventional manually applied clamps to block blood flow through the arterial lumen and a scalpel to make the elongated incision of the arteriotomy.
Beating heart surgical methods still use clamps and thus, still present the problems associated with clamps described above. For example, the common practice in beating heart surgical methods is to use a side-clamp rather than a cross-clamp. Beating heart surgical methods still require the creation of anastomosis and thus still require an aortotomy. Thus beating heart surgical methods still present the time constraints and difficulties associated with creating an effective anastomosis, such as difficulty creating an aortotomy hole with smooth edges and potential trauma resulting from clamping.
Several attempts have been made to create devices that occlude the vessel without using clamps or devices that maintain hemostasis of the aortotomy or arteriotomy during creation of an anastomosis.
U.S. Pat. Nos. 6,132,397 and 6,068,608 to Davis describes an aortic arch clamp catheter which occludes the ascending aorta using an expandable balloon rather than a cross clamp.
U.S. Pat. No. 6,165,196 to Stack et al. describes an occlusion apparatus with two occluding members and a shield that resists perforation.
U.S. Pat. No. 5,766,151 to Valley et al. describes a modified endovascularly inserted, internal vascular clamp to be used within the vessel instead of the external cross clamp.
Other methods and devices are described for creating effective anastomoses.
U.S. Pat. No. 6,193,734 to Bolduc et al. describes a device for creating anastomoses using a tissue securing member movable from a first to second configuration which movement causes a compressive force to be applied to the vessels to be joined.
U.S. Pat. No. 6,234,995 to Peacock describes a modified arterial catheter with a distal end portion that may be positioned within the aortic root adjacent to the left ventricle and a proximal portion that is coupled to a bypass pump.
U.S. Pat. No. 6,395,015 to Borst et al. and assigned to Medtronic describes a temporary intravascular arteriotomy seal for insertion into and retrieval from a blood vessel through an opening in the wall of the vessel.
U.S. Pat. No. 6,171,319 to Nobles and Baladi describes a device comprising an inverting member adapted to be inserted through a small incision in a blood vessel while the inverting member is maintained in an elongated, narrow configuration. A seal is then formed by applying a proximal force to the inverting member which has been inverted into an expanded, inward-facing cup following insertion into the blood vessel. The rim of the cup forms a seal against the inner wall of the blood vessel, thereby preventing blood from flowing out of the incision.
Instruments that combine the application of suction to the epicardial surface around or alongside the anastomosis site to suppress heart motion with a cutting mechanism for making the arteriotomy are disclosed in the above-referenced '175 and '770 patents. The surgical cutting instruments disclosed in the '770 and '175 patents include an elongated shaft having a proximal end, a distal end adapted for percutaneous insertion against the target coronary artery over the anastomosis site, and an axial lumen therebetween. A suction pad is formed at the distal end of the shaft, and a cutting element disposed within the lumen of the shaft near the distal end. A vacuum line is fluidly coupled to the lumen of the shaft and is adapted to connect to a vacuum source to effect a suction force at the distal end of the shaft. A control mechanism is provided to selectively block flow between the vacuum source and the lumen. The control mechanism may include a slide valve, an on/off button, or other equivalent mechanism for selectively closing and opening the vacuum pathway. A gripper assembly configured to grip a portion of the coronary artery is also disclosed in the '175 patent.
The cutting element and the shaft are relatively moveable between a retracted position and a cutting position. The cutting element is adapted to make the elongated slit of the arteriotomy in alignment with the axis of the coronary artery when the cutting element and the shaft are in the cutting position and the vacuum holds the anastomosis site steady.
The distal end of the shaft disclosed in the '175 patent has an outside diameter of less than about 5 mm, and the cutting element comprises at least one cutting element having a substantially straight blade cutting edge. The cutting edge is displaced at an angle of between about 15 to 30 degrees relative to a vertical axis through the cutting element. In one embodiment, the cutting element is fixed to an actuator push rod located within the lumen of the shaft, and connected to an actuator, preferably an actuator button, at a proximal end thereof. In another embodiment, the shaft is slidably mounted to a handle of the cutting instrument. An anchor, preferably a rigid rod coaxially disposed within the shaft, fixes the cutting element to the handle. An actuator member mounted to the shaft and biased by a spring is actuated to slide the shaft between retracted and cutting positions with respect to the cutting element.
Additionally or alternatively, at least one electrode may be disposed near the distal end of the shaft to effect or enhance cutting. The electrode may be operatively coupled to the cutting element, preferably substantially co-linearly coupled to the cutting edge. In the depicted embodiments, the electrode extends to the sharpened tip of the cutting element opposite to the cutting blade. In use, the end of the electrode at the tip of the cutting element is placed against the coronary artery and energized by radio frequency energy as the cutting element is moved to the cutting position to facilitate making a small point incision or pilot hole in the coronary artery. Then, the cutting blade is fully advanced to make the elongated cut. Ultrasonic energy may be applied to the cutting element to effect or enhance cutting by the ultrasonically vibrating the cutting blade.
The approaches described above for making an arteriotomy employ a cutting blade to make the elongated slit. In most cases, the shaft must be carefully moved to advance the cutting blade along the length of the vessel wall without inadvertently pushing the tip of blade across the vessel lumen and through the vessel wall opposite to the intended slit. Damage can be caused to the vessel wall if care is not taken.
An instrument or tool is needed for making an arteriotomy, an aortotomy or a similar incision in a vessel wall that avoids or minimizes the loss of blood through the incision.
An instrument or tool is needed that inhibits blood loss through the incision as an anastomosis is being made.
An instrument or tool is needed that reduces or eliminates the need for clamps.
An instrument or tool is also needed that reduces the time for creating an anastomosis.
All the publications and patents described above are hereby incorporated by reference herein in their respective entireties. As those of ordinary skill in the art will appreciate readily upon reading the Summary of the Invention, the Detailed Description of the Preferred Embodiments and the Claims set forth below, many of the devices and methods disclosed above may be modified advantageously by using the teachings of the present invention.